United Kingdom patent application GB-A-231546 proposes various arrangements whereby radio apparatus is used for transmitting data. The radio apparatus used comprises two elements, first, a radio device which is the source of the data to be transmitted, and secondly one or more antennae used for communication with the radio device. U.S. Pat. No. 6,217,683 to Balzer et al. discloses a monitoring device for a tire that is contained in a rigid package and mounted on a patch having a stand-off element.
While combinations of antennae and radio and/or sensor devices can readily be produced under laboratory conditions for testing purposes, implementation of antennae and radio device combinations in relatively hostile environments presents substantial practical difficulties.
One environment which gives rise to particular problems is that of vehicle tires. The electronic monitoring of tires, for identification and condition, has become important in recent years. Although a radio device may be used, for example, to generate radio signals indicative of the temperature or pressure within a vehicle tire or to provide information as to the history of usage of the tire, the environment of a vehicle tire presents a number of difficulties in the implementation of radio technology to communicate with the radio device. In particular, at the frequencies typically used for this type of radio device the antenna required will, in general, be flexible and will be several tens of centimeters in length. In contrast, the sensor package will be rigid and very small—typically less than 10 mm square and less than 5 mm thick.
Because of the size of the antenna it must, as a practical matter, be secured to or embedded in the material of the tire. This material is subject to significant flexing as the wheel carrying the tire rotates. This repeated flexing makes it very difficult to provide reliable connections between the antenna and the relatively small rigid package.
The present invention avoids the problem outlined above by providing self-contained radio apparatus for the transmission of data, the apparatus comprising: a resiliently deformable patch in which is embedded, or upon the surface of which is secured a deformable antenna: a stiffened region on one major face of the patch, the stiffened region providing a mounting for a radio device which provides data for transmission by the antenna; and electrical conductors extending from the antenna into the stiffened region for connection to the package.
The stiffened region resists bending to provide a protective mounting for the package, while the less stiff surrounding parts of the patch allow flexing for compliance with the tire. According to a first embodiment, the stiffened region is provided by a raised land portion, preferably to about twice the thickness of the surrounding patch area. Other manners of stiffening a region of the patch may be used, for example, ribs may be formed in the patch. Also, stiffening materials, such as fibers, may be incorporated in the stiffened region.
According to an alternative embodiment, the stiffened region may comprise a post upstanding from a major face of the patch, the post providing at the end thereof remote from the patch a mounting for the radio device. The provision of a post which is upstanding from one major surface of the patch provides a mounting means at the end thereof remote from the patch which is substantially de-coupled from the mechanical strain to which the patch may be subject in use. Essentially, even if the strain imposed on the patch is transmitted to the base of the post, very little of such strain will be transmitted to the end of the post remote from the patch.
In a particularly preferred embodiment of the invention the patch, including a raised land portion, ribs, or post, is formed integrally of a resiliently deformable material, for example a rubber.
In a particularly preferred use of the invention the patch is adhesively secured on the major surface thereof opposite to that from which the post extends to the inside of a tire. By suitably choosing the material of the patch, the patch will readily conform to the interior surface of the tire and can be adhesively bonded thereto using conventional adhesive techniques. The radio device may be secured to the post after the patch has been secured to the tire or, in the preferred embodiment, during manufacture of the apparatus. In other words, a complete radio apparatus comprising antenna and radio device is assembled with the patch and post during manufacture to produce a complete unit which can readily be retro-fitted to an existing tire by means of conventional adhesive techniques. The ability to provide the complete radio apparatus as a pre-formed assembly which can easily be secured in position using unskilled labor is a substantial practical advantage of the invention.